From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D8DB8C4363A for ; Wed, 21 Oct 2020 10:33:25 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 59D9C20795 for ; Wed, 21 Oct 2020 10:33:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="R7lUmo5u"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="ylezudmm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 59D9C20795 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:Message-ID:References:In-Reply-To:Subject:To:From: Date:MIME-Version:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=JnxgegoQJ3TDw+D5vjnaru2+G1zdPnZOQOClPQLgK78=; b=R7lUmo5uVrD6XtZSMXaQCqu/S EK9lkAdFkEiUjnnetupz79uoUEz/kcx3R9G1baJiNRfCb4M41cZVN5AP26wN5PzESNNINEdfmvOlJ TS+Uy4rH1uyHgWgEcGXc0gYmEzNaAJcaa/e6TLki/EuBGzm92FbBmJd/70CcvARCw3VSTLV3aXJHo EpvVjnlISzNTNI+JkISz8R8uKPdUyn14mo07Re+c2CRwz06L4UlXp8N1OVoBIGdgvd6i8nUPQbkn0 eJv1wF7b0MyttnDN0q2WiPnT1iyCIMQs7JmWn1F5N7D5T4Rgq2IcODlv75F5JFEh45DwRneMLhs3Z qDzKBzKGw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kVBPb-0006NR-2x; Wed, 21 Oct 2020 10:32:07 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kVBPX-0006MD-Kj for linux-arm-kernel@lists.infradead.org; Wed, 21 Oct 2020 10:32:05 +0000 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4B63A20795; Wed, 21 Oct 2020 10:32:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603276322; bh=9Wkyv/mfzZbVcmFZ4zwkkvY68hTmKXqXKL+Hf18lX7o=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ylezudmmKvIWzxnb+PQBmEHg54FcjvN5ArabT/9KI66kgjrw41HyXlGpEc91a8H33 uXALLRx4iq8qkzB9LZc9tX2wAHSA6zn9JopEYfC+cDXMvDUavFUCwjeqCUr8Z7AVt+ peAVp4v840PnF4XQV122yQjW8Iy0cJd+dIQr/HQ0= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1kVBPU-0030kr-8c; Wed, 21 Oct 2020 11:32:00 +0100 MIME-Version: 1.0 Date: Wed, 21 Oct 2020 11:32:00 +0100 From: Marc Zyngier To: Sumit Garg Subject: Re: [PATCH v5 5/5] arm64: ipi_nmi: Add support for NMI backtrace In-Reply-To: References: <1602673931-28782-1-git-send-email-sumit.garg@linaro.org> <1602673931-28782-6-git-send-email-sumit.garg@linaro.org> User-Agent: Roundcube Webmail/1.4.9 Message-ID: X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: sumit.garg@linaro.org, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, tglx@linutronix.de, jason@lakedaemon.net, mark.rutland@arm.com, julien.thierry.kdev@gmail.com, dianders@chromium.org, daniel.thompson@linaro.org, jason.wessel@windriver.com, msys.mizuma@gmail.com, ito-yuichi@fujitsu.com, kgdb-bugreport@lists.sourceforge.net, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201021_063204_715453_796B1A31 X-CRM114-Status: GOOD ( 24.42 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Daniel Thompson , Jason Cooper , Catalin Marinas , ito-yuichi@fujitsu.com, Douglas Anderson , Linux Kernel Mailing List , julien.thierry.kdev@gmail.com, Jason Wessel , kgdb-bugreport@lists.sourceforge.net, Thomas Gleixner , Masayoshi Mizuma , Will Deacon , linux-arm-kernel Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2020-10-20 10:13, Sumit Garg wrote: > On Mon, 19 Oct 2020 at 17:50, Marc Zyngier wrote: >> >> On 2020-10-14 12:12, Sumit Garg wrote: >> > Enable NMI backtrace support on arm64 using IPI turned as an NMI >> > leveraging pseudo NMIs support. It is now possible for users to get a >> > backtrace of a CPU stuck in hard-lockup using magic SYSRQ. >> > >> > Signed-off-by: Sumit Garg >> > --- >> > arch/arm64/include/asm/irq.h | 6 ++++++ >> > arch/arm64/kernel/ipi_nmi.c | 12 +++++++++++- >> > 2 files changed, 17 insertions(+), 1 deletion(-) >> > >> > diff --git a/arch/arm64/include/asm/irq.h >> > b/arch/arm64/include/asm/irq.h >> > index b2b0c64..e840bf1 100644 >> > --- a/arch/arm64/include/asm/irq.h >> > +++ b/arch/arm64/include/asm/irq.h >> > @@ -6,6 +6,12 @@ >> > >> > #include >> > >> > +#ifdef CONFIG_SMP >> > +extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask, >> > + bool exclude_self); >> > +#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace >> > +#endif >> > + >> > struct pt_regs; >> > >> > static inline int nr_legacy_irqs(void) >> > diff --git a/arch/arm64/kernel/ipi_nmi.c b/arch/arm64/kernel/ipi_nmi.c >> > index e0a9e03..e1dc19d 100644 >> > --- a/arch/arm64/kernel/ipi_nmi.c >> > +++ b/arch/arm64/kernel/ipi_nmi.c >> > @@ -9,6 +9,7 @@ >> > #include >> > #include >> > #include >> > +#include >> > #include >> > >> > #include >> > @@ -25,12 +26,21 @@ void arch_send_call_nmi_func_ipi_mask(cpumask_t >> > *mask) >> > __ipi_send_mask(ipi_desc, mask); >> > } >> > >> > +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool >> > exclude_self) >> > +{ >> > + nmi_trigger_cpumask_backtrace(mask, exclude_self, >> > + arch_send_call_nmi_func_ipi_mask); >> > +} >> > + >> > static irqreturn_t ipi_nmi_handler(int irq, void *data) >> > { >> > unsigned int cpu = smp_processor_id(); >> > >> > - ipi_kgdb_nmicallback(cpu, get_irq_regs()); >> > + if (nmi_cpu_backtrace(get_irq_regs())) >> > + goto out; >> > >> > + ipi_kgdb_nmicallback(cpu, get_irq_regs()); >> > +out: >> > return IRQ_HANDLED; >> > } >> >> Can't you have *both* a request for a backtrace and a KGDB call? >> It really shouldn't be either/or. It also outlines how well shared >> interrupts work with edge triggered signalling... > > Unfortunately, NMIs doesn't seem to support shared mode [1]. You are totally missing the point: shared interrupts *cannot* work reliably with edge signalling. What I am saying here is that you need implement the sharing yourself in this function. M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel